Differences Between Table Operators and Table Functions
The main differences between table functions and user‑defined table operators are as follows.
For a table operator, the iterator is the responsibility of the coder. The table operator itself is just called once.
Because the table operator itself has to do the iteration, it should be structured the way a simple AMP step is structured. The writer is provided with a row read/row write interface.
The parser function is similar to the standard scalar UDF in that it accesses one set of arguments (the input column types, and invocation metadata) and returns the list of output column types. However, like table functions, the output table format can also be determined by user specification at run time.